A nurse is caring for a client who has a prescription for levothyroxine. Which of the following laboratory tests should the nurse monitor?

A. Blood urea nitrogen measures kidney function, is not related to thyroid health. B. Arterial blood gases are used to assess oxygen and carbon dioxide levels in the blood, not related to thyroid health. C. Prothrombin time is a test used to assess blood clotting, not related to thyroid health. D. Correct. Monitoring thyroid stimulating hormone (TSH. levels is crucial for assessing the function of the thyroid gland and adjusting levothyroxine dosage as needed.